Due to recent improvements in combustion engine technology, there has been a trend to downsize internal combustion engines used in vehicles. Such improvements also result in more efficient vehicle, while maintaining similar performance characteristics and vehicle form factors favoured by consumers
One common improvement used with internal combustion engines is the addition of a supercharger or a turbocharger. Typically, the addition of the supercharger or the turbocharger is used to increase a performance of an engine that has been decreased in displacement or a number of engine cylinders. Such improvements typically result in an increased torque potential of the engine, enabling the use of longer gear ratios in a transmission of the vehicle. The longer gear ratios in the transmission enable engine down-speeding. Engine down-speeding is a practice of operating the engine at lower operating speeds. Such improvements typically result in improved fuel economy, operation near their most efficient level for a greater amount of time compared to conventional engines, and reduced engine emissions.
In some designs, however, engine down-speeding can result in an undesirable increase in torque ripple at low operating speeds of the engine. For example, a significantly increased torque ripple can appear at an engine output when the engine is operating at low idle speeds. The torque ripple is a well-known engine dynamic that results from torque not being delivered constantly, but periodically during each power stroke of the operating cycle of an internal combustion engine. FIG. 1 is a graph illustrating a torque output of an engine during a four stroke cycle of an engine. In the four stroke cycle, the torque ripple happens once every two turns of a crankshaft for each cylinder of the engine. Accordingly, a four cylinder engine will have two torque ripples per crankshaft turn while a three cylinder engine will have three ripples every two crankshaft turns.
An amplitude of the torque ripple also varies with an operating speed of the engine and a load applied to the engine. A phase of the torque ripple varies with an operating speed and a load applied to the engine. Torque ripples can cause many problems for components of the vehicle near the engine, such as but not limited to: increased stress on the components, increased wear on the components, and exposure of the components to severe vibrations. These problems can damage a powertrain of the vehicle and result in poor drivability of the vehicle. In order to reduce the effects of these problems, smooth an operation of the engine, and improve an overall performance of the engine, the torque ripples may be compensated for using an engine balancing method. Many known solutions are available for multi-cylinder engine configurations to reduce or eliminate the stresses and vibration caused by the torque ripples.
Torque ripple compensator devices are known in the art; however, the known device have many shortcomings. In many conventional vehicles, the torque ripples are compensated for using at least one flywheel. FIG. 2 illustrates a conventional flywheel based damping system. In other applications, a dual-mass flywheel system may be used. An inertia of the flywheel dampens a rotational movement of the crankshaft, which facilitates operation of the engine running at a substantially constant speed. Flywheels may also be used in combination with other dampers and absorbers.
A weight of the flywheel, however, can become a factor in such torque ripple compensating devices. A lighter flywheel accelerates faster but also loses speed quicker, while a heavier flywheel retain speeds better compared to the lighter flywheel, but the heavier flywheel is more difficult to slow down. However, a heavier flywheel provides a smoother power delivery, but makes an associated engine less responsive, and an ability to precisely control an operating speed of the engine is reduced.
In addition to a weight of the flywheel, another problem with conventional inertia and damping systems is a lack of adaptability. The conventional inertia and damping systems are designed for the worst operational condition and must be large enough to dampen vibrations at lower operating speeds. As a result, the conventional inertia and damping systems are not optimized for higher operating speeds, resulting in inadequate performance.
It would be advantageous to develop a torque ripple compensating device able to be passively or dynamically adapted for both an amplitude and a phase of a torque ripple while minimizing an interference with an operation of an internal combustion engine.